1. Field of the Invention
The present invention relates to an organic substance analyzing system for identifying and quantifying organic substances adhering to the surface of a sample such as a semiconductor wafer.
2. Background Art
Semiconductor devices have been progressively miniaturized in recent years, and it has been realized that the adhesion of organic contaminant substances to the surface of a semiconductor wafer deteriorates the characteristics of the devices heavily, which has not been much of a problem so far. Accordingly, in order to identify the organic substances which deteriorate the device characteristics, it is being requested to establish testing techniques for identifying and quantifying organic substances adhering to the surface of a semiconductor wafer.
Organic substance analyzing methods generally used at present are methods such as GC/MS (Gas Chromatograph Mass Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), FT-IR (Fourier Transform-Infrared Spectroscopy), SIMS (Secondary Ion Mass Spectrometry), NMR (Nuclear Magnetic Resonance), and Contact Angle Measuring Method. Among those methods, the GC/MS has become used most widely with establishment of measuring techniques because of its high detection sensitivity, its high ability to identify the kinds of organic substances and the easiness with which the measurement is made.
FIG. 7 shows a wafer heating unit used in a conventional GC/MS measuring apparatus. A whole surface of a wafer 2 placed in a chamber 1 is heated from the rear side thereof by a heater 3. A carrier gas is supplied through a carrier gas supply pipe 4, and gases discharged out of the heated wafer 2 are collected by a discharged gas collecting means 6 including a discharged gas collecting pipe 5. A discharged gas analyzing means 7 concentrates and separates the collected gases, and analyzes the resultant gases.
As described, the GC/MS method is widely used at present for identifying and quantifying organic substances adhering to the surface of a wafer, thus analyzes the gases discharged when the whole surface of the wafer is heated from its rear side.
In a wafer actually fabricated, however, organic substances adhering to the surface of the wafer are not necessarily uniformly adhered. For example, if a wafer is contaminated by discharged gases of organic substances adhering to a cassette for holding the wafer, more organic substances are adhered in portions in which the wafer is contact with the cassette. Thus, an analyzing techniques for local organic substance has to be established to elucidate the behavior of organic substances locally adhering to a wafer.
With the progress of further miniaturization of the devices, there appears a possibility that organic substances become a main cause for the deterioration of the device characteristics, although up to now the organic substances have been considered to exert less influence on the device characteristics compared with contamination substances such as metals and particles. If, in such a case, the local organic substance analysis is to be performed, a map checking of defective portions becomes possible, and the defect analysis may be performed in more detail and more effectively.